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Full text of "Text Book Of Mechanical Engineering"

Appendix   VI.

1209

water enters at F, and passing the first wheel H, travels along the
passages K p to wheel j, whence it escapes at G. The end view
will serve for both pumps. The wheel M, rotating in the direction
shewn, gives the water both tangential and radial flow. As it is
desired that the fluid shall be simply pressed forward radially and
quietly, the tangential velocity is next eliminated by the relative
back action of the guide blades N, fixed in the casing, and having
an inclination opposed to the wheel motion. The principle is
simply that of a reversed water turbine, and such pumps are
generally spoken of as turbine pumps. The axial balance piston
was introduced by Rateau, and the back-to-back wheels by
Sulzer. The latter are equally applicable to many stages, but
must be so arranged that half the wheels point in the opposite
direction to the other half. The guide blades are an old principle
revived.

The efficiencies in compound pumps at high lifts are very
good, while those on p. 734 for single wheels only reach their
maximum at low lifts. As to actual work, a 20 in. six-stage pump